Friction factors and drag coefficients of pneumatic pipeline capsules

Published

1 January 1983

ISBN

0305-1293

Author

Bunce, JA

Pages

40

Reference

SR772

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Wheeled cargo-carrying capsules are propelled through a pipeline by a current of air. Air pressure and flow rate for a given capsule throughout depend on the capsule speed and on parameters of capsule and pipeline. The relation of pressure and flow (and hence of pneumatic power input) to speed and gradients is first examined with the simplifying assumptions that the resistance of a capsule is proportional to the mass and that the leakage past a capsule is proportional to the square root of the pressure-drop across it. Analysis of experimental data leads to revision of these assumptions in which resistance and leakage factors vary with mass and speed. It is concluded that power demand will increase with speed more steeply than the simplified theory would predict, and that reduced leakage might be associated with a disproportionate increase in frictional resistance. This will favour the use of a lower operating speed. (A)